Take a look at the sentence again:
The blonde who sucked the ends of her hair, the athlete who blinked nervously,
and __________ would not share their algebra homework with Jake.
The blank requires a noun followed by an adjective clause. You chose the rebel slouching in his seat, which is a noun followed by a participle phrase. You thus have a parallelism error on your hands. Before you continue, review the rules for parallel structure.
Go back to the sentence to try again.